Striped pattern image examination support apparatus, striped pattern image examination support method, and program

ABSTRACT

A striped pattern image examination support apparatus includes a feature extraction part, a central line collation part, and a display part. The feature extraction part extracts, from each of a first striped pattern image and a second striped pattern image, at least central lines and feature points, as a feature of each of the first striped pattern image and the second striped pattern image. The central line collation part performs collation of the respective central lines of the first striped pattern image and the second striped pattern image, and computes corresponding central lines between the first striped pattern image and the second striped pattern image. The display part determines a display form of each of the central lines based on the computed corresponding central lines and superimposes and displays the central lines on each of the first striped pattern image and the second striped pattern image, according to the determined display form.

TECHNICAL FIELD Cross-Reference to Related Applications

The present invention is based upon and claims the benefit of thepriority of Japanese Patent Application No. 2016-209502 (filed on Oct.26, 2016), the disclosure of which is incorporated herein in itsentirety by reference. The present invention relates to a stripedpattern image examination support apparatus, a striped pattern imageexamination support method, and a program. More specifically, theinvention relates to a striped pattern image examination supportapparatus, a striped pattern image examination support method, and aprogram for supporting examination of two images such as fingerprints orpalmprints (determination whether the striped pattern images areidentical or not).

BACKGROUND ART

A fingerprint composed of a lot of ridges in a striped pattern is saidto have two remarkable features that the fingerprint is invariantthroughout life and is not the same for anyone. Thus, the fingerprinthas been used as means for personal identification for a long time.

In a fingerprint examination or a difference determination offingerprints as to whether or not two fingerprints belong to a samefinger, an examiner (examiner) looks and compares two fingerprint imagesand visually determines whether or not feature points are present atcorresponding positions on ridges of the two fingerprints. If the numberof the feature points that become pairs between the two fingerprints orthe feature points that are present at the corresponding positions onthe ridges of the two fingerprints is a certain number or more, it isdetermined that the two fingerprints belong to the same finger. Theridges are linear elevations that are present on the skin of a finger ora palm, or a striped pattern in a fingerprint or a palmprint that hasbeen applied by the linear elevations.

In a fingerprint image or a palmprint image, a feature point oftenindicates an ending point or a bifurcation point of a ridge thatconstitutes a stripe. Feature points that become a pair in two images(fingerprint images in this case) are referred to as paired featurepoints.

A material indicating a relation between paired feature points that havebeen confirmed is presented in a trial or the like, together with twofingerprint photographs and fingerprint grayscale images that have beendisposed side by side. Non Patent Literature 1 describes an example ofthe material that is presented in the trial, for example.

In recent years, a fingerprint collation system using a computingmachine (such as an information processing apparatus or a computer) hasbeen spreading. Therefore, an evidentiary material for a trial is oftenprepared by using the computer. Usually, a work of displaying twofingerprint images side by side, connecting paired feature points on thetwo fingerprint images by a line, and describing a number given to thepaired feature points is referred to as charting. A function ofdisplaying two fingerprints and supporting manual input or modificationof the paired feature points in a system for preparing the material forthe trial using the computer is referred to as a charting function(Charting Function).

The computing machine including the charting function often displays twofingerprints for a difference determination from side from side. Such adisplay method is referred to as a side by side (side by side) display.Diagrams or screens for which the side by side display has beenperformed is also referred to as a charting diagram or a feature pointchart diagram. On a charting screen, a line connecting two correspondingfeature points is also often displayed.

When confirming corresponding feature points, usually, an examinervisually confirms whether ridges that are present in the vicinity of thefeature points of interest on two fingerprint images for examination areidentical or not. When two fingerprints for the examination includingthe vicinity ridges match, the examiner determines that the confirmedcorresponding feature points are correct. However, it is not easy todetermine whether the ridges that are present in the vicinity of thefeature points of interest are identical or not.

In a trial having a jury system such as the one in the United States,explanation of fingerprint identicalness to a jury (non-expert of afingerprint) is required. It is not, however, easy to explain to such anon-expert about determination whether ridges are identical or not.Then, Non Patent Literature 2 proposes a method of coloringcorresponding ridges in order to facilitate determination whether ridgesin the vicinity of feature points are identical or not.

CITATION LIST Non Patent Literature

-   [NPL 1] Page 193-196 of “The science of Fingerprints Classification    and Uses” (by John Edgar Hoover, US DOJ, FBI; Rev. 12-84, 1990)-   [NPL 2] VanDam Page—Updated 3-28-06, “a place for Friction Ridge    Examiners to access information about the discipline of Friction    Ridge and Latent Print Examination”, [online], [searched on Oct. 12,    2016], Internet <URL: http://www.clpex.com/VanDam.htm>

SUMMARY OF INVENTION Technical Problem

Each disclosure of the above-listed Citation List is incorporated hereinin its entirety by reference. The following analysis has been made bythe inventors of the present invention.

The surface of a finger or a palm is soft and easy to be deformed. Thus,it is usual that even if a same finger or a same palm is used, the shapeof a fingerprint or a palmprint taken as an image is different for eachimage. Consequently, even if two fingerprint images or two palmprintimages for examination are generated from an identical fingerprint or anidentical palmprint, ridges are not overlapped with each other even bytranslation or rotation.

Further, when a region with an unclear ridge is included due to badquality of a fingerprint image, for instance, in such a case as when oneof fingerprint images for examination is a remaining fingerprint, it isdifficult to determine whether individual ridges in the vicinity offeature points are identical or not, so that an erroneous determinationmay be performed for fingerprints as a whole.

In the method of distinguishing the corresponding ridges by using acolor described in Non Patent Literature 2, determination whether theindividual ridges in the vicinity of the feature points are identical ornot can be clearly made. Determination whether whole fingerprints areidentical or not can be thereby facilitated. However, this method iscarried out by manually performing coloring of the individual ridgesusing a commercial graphic tool, so that a lot of man-hours arerequired.

It is an object of the present invention to provide a striped patternimage examination support apparatus, a striped pattern image examinationsupport method, and a program for supporting striped pattern imageexamination of determining whether or not two striped pattern images aregenerated from a same object.

Solution to Problem

According to a first aspect of the present invention or disclosure,there is provided a striped pattern image examination support apparatuscomprising:

a feature extraction part to extract at least central lines and featurepoints from each of first and second striped pattern images, as afeature of each of the first and second striped pattern images;

a central line collation part to perform collation of the respectivecentral lines of the first striped pattern image and the second stripedpattern image and compute corresponding central lines between the firstand second striped pattern images; and

a display part to determine a display form of each of the central linesbased on the computed corresponding central lines and superimpose anddisplay the central lines on each of the first and second stripedpattern images, according to the determined display form.

According to a second aspect of the present invention or disclosure,there is provided a striped pattern image examination support methodcomprising the steps of:

extracting at least central lines and feature points from each of firstand second striped pattern images, as a feature of each of the first andsecond striped pattern images;

performing collation of the respective central lines of the firststriped pattern image and the second striped pattern image and computingcorresponding central lines between the first and second striped patternimages; and

determining a display form of each of the central lines based on thecomputed corresponding central lines and superimposing and displayingthe central lines on each of the first and second striped patternimages, according to the determined display form.

According to a third aspect of the present invention or disclosure,there is provided a program configured to cause a computer to execute:

a process of extracting at least central lines and feature points fromeach of first and second striped pattern images, as a feature of each ofthe first and second striped pattern images;

a process of performing collation of the respective central lines of thefirst striped pattern image and the second striped pattern image andcomputing corresponding central lines between the first and secondstriped pattern images; and

a process of determining a display form of each of the central linesbased on the computed corresponding central lines and superimposing anddisplaying the central lines on each of the first and second stripedpattern images, according to the determined display form.

This program can be recorded on a computer-readable storage medium. Thestorage medium can be set to a non-transient (non-transient) one such asa semiconductor memory, a hard disk, a magnetic recording medium, or anoptical recording medium. The present invention can also be embodied asa computer program product.

Advantageous Effects of Invention

According to each aspect of the present invention, there are provided astriped pattern image examination support apparatus, a striped patternimage examination support method, and a program for supporting stripedpattern image examination to determine whether or not two stripedpattern images are the ones generated from a same object.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for explaining an overview of an exemplaryembodiment.

FIG. 2 is a diagram illustrating an example of a configuration of astriped pattern image examination support apparatus according to a firstexemplary embodiment.

FIG. 3 is a block diagram illustrating an example of a hardwareconfiguration of the striped pattern image examination support apparatusaccording to the first exemplary embodiment.

FIG. 4 is a flowchart illustrating an example of operations of thestriped pattern image examination support apparatus according to thefirst exemplary embodiment.

FIG. 5 is a diagram illustrating an example of a remaining fingerprint.

FIG. 6 is a diagram illustrating an example of an impressionfingerprint.

FIG. 7 includes FIG. 7A and FIG. 7B in which FIG. 7A is a diagram whereextracted central lines are superimposed on the remaining fingerprintillustrated in FIG. 5, and FIG. 7B is a diagram where extracted featurepoints and so on are superimposed on the remaining fingerprintillustrated in FIG. 5.

FIG. 8 includes FIG. 8A and FIG. 8B in which FIG. 8A is a diagram whereextracted central lines are superimposed on a fingerprint imageillustrated in FIG. 6, and FIG. 8B is a diagram where extracted featurepoints and so on are superimposed on the fingerprint image illustratedin FIG. 6.

FIG. 9 is a diagram illustrating an example of a feature point chartdiagram.

FIG. 10 includes FIG. 10A and FIG. 10B that constitute a diagramillustrating an example of a ridge chart diagram in which ridge chartsare superimposed on each of FIG. 7A and FIG. 8A.

FIG. 11 includes FIG. 11A and FIG. 11B in which FIG. 11A is a diagramillustrating an example where, with respect to five feature pointsillustrated in FIG. 9 and having the different feature point types, thefeature point types in the remaining fingerprint have been manuallymodified by a user, and FIG. 11B is a diagram for explaining generationof each central line that matches a manual feature point.

FIG. 12 includes FIG. 12A and FIG. 12B that are diagrams eachillustrating correspondence relationships between central lines afterthe feature point modification.

FIG. 13 includes FIG. 13A and FIG. 13B for explaining an operation of aridge chart modification part.

DESCRIPTION OF EMBODIMENTS

First, an overview of an exemplary embodiment of the present inventionwill be described. A reference numeral in each drawing given in thisoverview is given to each element for convenience as an example forhelping understanding, and the description of this overview does notintend to impose any limitation.

A striped pattern image examination support apparatus 100 according tothe exemplary embodiment includes a feature extraction part 101, acentral line collation part 102, and a display part 103. The featureextraction part 101 extracts at least central lines and feature pointsfrom each of a first striped pattern image and a second striped patternimage as a feature of each of the first striped pattern image and thesecond striped pattern image. The central line collation part 102performs collation of the respective central lines of the first stripedpattern image and the second striped pattern image, thereby computingcorresponding central lines between the first and second striped patternimages. The display part 103 determines the display form of each of thecentral lines based on the computed corresponding central lines andsuperimposes and displays the central lines on each of the first andsecond striped pattern images, according to the determined display form.

The striped pattern image examination support apparatus 100 computes thecentral lines (corresponding central lines; ridge charts) thatconstitute a pair between two striped pattern images. Then, based on thecomputed corresponding central lines, the striped pattern imageexamination support apparatus 100 selects the display form of each ofthe lines to be displayed on each of the two striped pattern images. Totake an example, the striped pattern image examination support apparatus100 distinguishes the corresponding central lines and a noncorrespondingcentral line (central line of one of the two images for which a centralline that becomes a pair between the two images does not present on theother image) by using different colors, thereby allowing distinctionbetween the corresponding central lines and the noncorresponding centralline by a user (such as an examiner). Alternatively, the striped patternimage examination support apparatus 100 highlights the noncorrespondingcentral line among the central lines included in each of the two stripedpattern images, thereby allowing recognition of the presence of thenoncorresponding central line by the user.

By checking the display that is presented by the striped pattern imageexamination support apparatus 100, the user can readily determinewhether or not the two fingerprint images indicate fingerprints of asame finger. That is, if there is no noncorresponding central line, theuser can readily determine that the two images are images of the samefinger. As mentioned above, the striped pattern image examinationsupport apparatus 100 is an apparatus configured to support examinationas to whether the two fingerprint images indicate the fingerprints ofthe same finger and can reduce burden on a work of checking whetherridges are identical or not by the examiner.

Hereinafter, a specific exemplary embodiment will be described infurther detail, with reference to the drawings. A same reference numeralis given to same components in the respective exemplary embodiments, anddescription of the same components will be omitted. A connection linebetween blocks in each drawing includes both of a bidirection and amonodirection. A one-way arrow schematically illustrates a main signal(data) stream and does not exclude bidirectionality.

First Exemplary Embodiment

A striped pattern image examination support apparatus according to afirst exemplary embodiment will be described in detail with reference tothe drawings.

FIG. 2 is a diagram illustrating an example of a configuration of astriped pattern image examination support apparatus 10 according to thefirst exemplary embodiment. A display device 20 such as a display and aninput device 30 such as a keyboard, a mouse, or a tablet are connectedto the striped pattern image examination support apparatus 10.

A striped pattern image is an image including a curved stripe patternformed by ridges. To take an example, a fingerprint image or a palmprintimage including a region of a fingerprint or a palmprint is the stripedpattern image. The striped pattern image may be, however, an image of astripe including an ending point or a bifurcation point and is notlimited to the fingerprint image or the palmprint image.

Corresponding ridges (ridge charts) refers to ridges, among ridgesincluded in two striped pattern images, which have been determined to bethe ridges extracted from locations of a same stripe pattern (or to becorresponding) between the two striped pattern images. Hereinafter, whenit has been written just as a “ridge chart”, the “ridge chart”indicates, out of corresponding ridges between the two striped patternimages, a ridge on one of the two striped pattern images. When it hasbeen written as a “ridge chart pair”, the “ridge chart pair” indicates apair of a ridge on one image and a ridge on the other imagecorresponding to the ridge on the one image. When it has been written asa “plurality of ridge charts”, the “plurality of ridge charts” indicatea plurality of ridges which are included in one image and to which acorresponding ridge is present in the other image. Usually, a centralline is a skeletal line that is extracted from a ridge. In thedisclosure of the present application, a ridge and a central line aretreated to be the same unless otherwise specifically noted. That is, aridge chart may indicate a corresponding central line (correspondingcentral line).

A central line and a feature point may be the ones automaticallyextracted from a striped pattern image by a computing machine or thelike, using an existing arbitrary method, or may be the ones selected bya user or the like. Determination as to correspondence of central linesincluded in the two striped pattern images may be automatically made bythe computing machine or the like, using an existing arbitrary method,or may be manually made by the user or the like.

[Hardware Configuration]

Subsequently, a hardware configuration of the striped pattern imageexamination support apparatus 10 according to the first exemplaryembodiment will be described.

FIG. 3 is a block diagram illustrating an example of the hardwareconfiguration of the striped pattern image examination support apparatus10 according to the first exemplary embodiment.

The striped pattern image examination support apparatus 10 isimplemented by a so-called information processing apparatus (computer),and includes the configuration illustrated in FIG. 3, for example. Thestriped pattern image examination support apparatus 10 includes a CPU(Central Processing Unit) 91, a memory 92, an input/output interface 93,and an NIC (Network Interface Card) 94 that is communication means, andso on, which are mutually connected by an internal bus.

The configuration illustrated in FIG. 3, however, does not intend tolimit the hardware configuration of the striped pattern imageexamination support apparatus 10. The striped pattern image examinationsupport apparatus 10 may include hardware not illustrated or may notinclude the NIC 94 or the like, as necessary. It does not also mean thatthe number of CPUs or the like that are included in the striped patternimage examination support apparatus 10 is not limited to theillustration in FIG. 3, and a plurality of of the CPUs, for example, maybe included in the striped pattern image examination support apparatus10.

The memory 92 is a RAM (Random Access Memory), a ROM (Read Only Memory),or an auxiliary storage device (such as a hard disk).

The input/output interface 93 is means for serving as an interface forthe display device 20 and the input device 30. The display device 20 isa liquid crystal display or the like, for example. The input device 30is a device configured to accept a user operation using a keyboard or amouse. An external storage device such as a USB (Universal Serial Bus)memory can be included in the input device 30.

Functions of the striped pattern image examination support apparatus 10are implemented by various processing modules that will be describedlater. The processing modules are implemented by execution of a programstored in the memory 92 by the CPU 91. That program can be downloadedvia a network or can be updated using a storage medium that has storedthat program. The processing modules may be implemented by asemiconductor chip. That is, means for executing the functions of theprocessing modules using certain hardware and/or software may beprovided.

Subsequently, processing configurations (of processing modules) of thestriped pattern image examination support apparatus 10 according to thefirst exemplary embodiment will be described. Referring to FIG. 2, thestriped pattern image examination support apparatus 10 is configured byincluding a feature extraction part 11, a central line collation part12, a ridge chart diagram display part 13, a feature modification part14, and a ridge chart modification part 15.

The feature extraction part 11 is means for extracting at least centrallines and feature points from each of two striped pattern images, as afeature of each of the two striped pattern images. That is, the featureextraction part 11 is means for extracting from an image that is inputto the striped pattern image examination support apparatus 10, a featureamount (such as the central lines and the feature points) that featuresthe image. To take an example, the feature extraction part 11 extractscentral lines and feature points from each of a striped pattern image Aand a striped pattern image B, as illustrated in FIG. 2. The featureextraction part 11 also extracts ridge zones (zones) in the extractionprocess of the feature points.

Further, as will be described later, when the user manually modifies orinputs a feature point (such as in a case where the user has deleted oradded the feature point), the feature extraction part 11 executesextraction of a central line holding the feature point that has beenmanually modified. Similarly, when the user manually modifies or inputsa central line or a zone, the feature extraction part 11 executesextraction of a feature point holding the central line or the zone. Thatis, the feature extraction part 11 is also means for extracting thecentral line again while holding the feature of a striped pattern imagethat has been modified by the user.

The central line collation part 12 is means for performing collation ofthe respective central lines of the two striped pattern images andcomputing corresponding central lines between the striped patternimages. That is, the central line collation part 12 performs collationof the central lines extracted from the two striped pattern images andoutputs the corresponding central lines (corresponding central lines:ridge charts). The central line collation part 12 is also means forcomputing corresponding central lines again from the two striped patternimages using the central line extracted again by the feature extractionpart 11.

The ridge chart diagram display part 13 is means for superimposing anddisplaying the central lines on each striped pattern image. Whendisplaying the ridge charts, the ridge chart diagram display part 13displays a ridge chart pair (the respective corresponding central linesof the two striped pattern images) using a same color and a same linetype, thereby demonstrating a correspondence relationship in a ridgechart diagram. The ridge chart diagram display part 13 displays, side byside, (performs side-by-side display of) striped pattern images eachwith the ridge chart distinguished by the same color or the same linetype superimposed thereon in order to demonstrate the correspondencebetween the two striped pattern images and the ridge charts. Such adiagram is referred to as the ridge chart diagram.

In addition to the display of the corresponding central line of each ofthe striped pattern images using the same color or the like as mentionedabove, the ridge chart diagram display part 13 can take various measureswhen the ridge chart diagram display part 13 displays the ridge chartdiagram. To take an example, the ridge chart diagram display part 13 cansuperimpose a certain one of a plurality of central lines computed fromeach striped pattern image on the striped pattern image by using apredetermined form (can perform a display for a corresponding centralline) if the certain central line is the corresponding central line. Ifanother one of the central lines is a noncorresponding central line, theridge chart diagram display part 13 can superimpose the another centralline on the striped pattern image by using a predetermined display forthe noncorresponding central line. To take an example, the ridge chartdiagram display part 13 may distinguish the corresponding central lineand the noncorresponding central line that have been extracted from thestriped pattern image by using different colors and may superimpose thecorresponding central line and the noncorresponding central line on thestriped pattern image. Further, on that occasion, the color or the linetype of each of the corresponding central line and the noncorrespondingcentral line to be superimposed on each striped pattern image may bemade common between the two striped pattern images. Alternatively, theridge chart diagram display part 13 may highlight and display thenoncorresponding central line among the central lines extracted from thestriped pattern images. The form (such as a change in the color of eachcentral line or a change in the line type of the central line) by whichthe ridge chart diagram display part 13 superimposes and displays eachcentral line on each striped pattern image may be set in advance, or maybe determined by the user, using a menu or the like. The display form ofeach central line includes a form by which the central line is notdisplayed (not superimposed) on each striped pattern image. That is,only the noncorresponding line may be highlighted and displayed on eachstriped pattern image so that the user can immediately grasp thepresence of the noncorresponding line.

As mentioned above, when displaying the ridge chart diagram, the ridgechart diagram display part 13 uses the corresponding central linescomputed by the central line collation part 12. Specifically, the ridgechart diagram display part 13 refers to information on theabove-mentioned computed corresponding central lines and determineswhether or each of the plurality of central lines included in eachstriped pattern image is the “corresponding central line” or the“noncorresponding central line”. Then, based on a determination resultabout each central line, the ridge chart diagram display part 13determines the display form (such as the color or the line type of eachcentral line) when the central line is superimposed on the stripedpattern image, and displays the ridge chart diagram. That is, the ridgechart diagram display part 13 determines the display form of eachcentral line based on whether or not the central line is thecorresponding central line, and superimposes and displays the centralline on the striped pattern image by the determined display form.

When the corresponding central lines are computed again by the centralline collation part 12, the ridge chart diagram display part 13determines the display form of each central line to be superimposed oneach of the two striped pattern images, based on the correspondingcentral lines.

The ridge chart diagram display part 13 performs display of the ridgechart diagram on the display device 20 such as the display. The ridgechart diagram display part 13 may display a feature point chart diagram(refer to FIG. 9), as necessary.

The feature modification part 14 is means for performing featuremodification of at least one of the two striped pattern images.Specifically, the feature modification part 14 independently performsfeature modification such as a change in the type of a feature point,addition or deletion of a feature point, addition or deletion of acentral line, addition or deletion of a zone, or the like for each ofthe two striped pattern images, by an operation by the user who has usedthe input device 30.

Further, the feature modification part 14 includes a function ofautomatically updating a feature point type in one of the stripedpattern images to a feature point type in the other of the stripedpattern images when the types of paired feature points respectivelyincluded in the two striped pattern images are mutually different. Thatis, when the feature point type such as an ending point or a bifurcationpoint is different between corresponding feature points between the twostriped pattern images, the feature point modification part 14 can alsoupdate the feature point type of one of the two striped pattern imagesby the feature point type of the other of the two striped patternimages.

The ridge chart modification part 15 is means for changing the colortype or the line type of the ridge chart and performing modificationsuch as addition of a ridge chart or deletion of the ridge chart, by anoperation by the user who has used the input device 30 that is akeyboard or a pointing device such as a mouse or a tablet. Since theridge chart is associated between the two images, the ridge chartmodification part 15 performs addition of the ridge chart and deletionof the ridge chart using both of the images. That is, the ridge chartmodification part 15 is also means for accepting an operation by theuser for changing the display form of the corresponding central line onthe ridge chart diagram (of the two striped pattern images each with thecentral lines superimposed and displayed thereon) displayed by the ridgechart diagram display part 13.

Subsequently, the first exemplary embodiment will be described withreference to a flowchart illustrated in FIG. 4 and the drawingsindicating examples of fingerprint images. On that occasion, adescription will be given about a case where a ridge chart diagram of aremaining fingerprint illustrated in FIG. 5 and an impressionfingerprint (impression fingerprint that becomes a pair of the remainingfingerprint in FIG. 5) illustrated in FIG. 6 is displayed by the stripedpattern image examination support apparatus 10 according to the firstexemplary embodiment.

Referring to FIG. 4, the feature extraction part 11 of the stripedpattern image examination support apparatus 10 first receives twostriped pattern images (step S10). The striped pattern images that arereceived by the striped pattern image examination support apparatus 10may be obtained from an image input device such as a sensor or ascanner, or image data digitized and stored in advance may be obtained,using a USB memory or the like.

The remaining fingerprint is a fingerprint that has been left on a crimescene or the like, for example, and often has a poor quality. Oncontrast therewith, the impression fingerprint is a fingerprint takenfor a registration purpose, and often has a good quality. Fingerprintsfor determination whether the fingerprints are identical or not may beremaining fingerprints or impression fingerprints. However, thedetermination whether the fingerprints are identical or not is oftenmade between the remaining fingerprint and the impression fingerprint.

Examples of fingerprint images illustrated in FIGS. 5 and 6 and so onare obtained by digitizing fingerprint images read by a sensor or ascanner. The examples of the fingerprint images as mentioned above areobtained by the digitization with a resolution of 500 dpi, according to“ANSI/NIST-ITL-1-2000 Data Format for the Interchange of Fingerprint,Facial & Scar Mark & Tattoo (SMT) Information” that has beenstandardized at the NIST (National Institute of Standards andTechnology) in the United States. The above-mentioned document on thestandardization is disclosed in NIST Special Publication 500-245 inANSI/NIST-ITL 1-2000 Revision of ANSI/NIST-CSL1-1993 & ANSI/NIST-ITL1a-1997 (the URL for the document is<https://www.nist.gov/sites/default/files/documents/itl/ansi/sp500-245-a16.pdf)>.

Subsequently, the feature extraction part 11 extracts a feature (featureamount) of the fingerprint from each of the fingerprint images in FIGS.5 and 6 (step S11). The feature of the fingerprint includes centrallines and zones (ridge regions), in addition to feature points. Usually,feature point extraction is performed by thinning (central lineformation of) each stripe included in a digitized striped pattern imageand extracting an ending point and a bifurcation point from each centralline obtained by thinning the stripe. The feature point extractionincluding the central line formation can be implemented, using a methoddescribed in Reference Literature 1 of “Handbook of FingerprintRecognishon p 83-113, D. Maltoni, et. al., Spinger”.

When the feature extraction process in step S11 is executed for theremaining fingerprint illustrated in FIG. 5, images illustrated in FIG.7 are obtained. FIG. 7A illustrates an example where the extractedcentral lines are superimposed on the fingerprint image illustrated inFIG. 5. FIG. 7B illustrates an example where the extracted featurepoints and zones are superimposed on the fingerprint image in FIG. 5.With respect to the zones, regions that could not be recognized asridges are displayed after having been filled in such a manner that theregions can be distinguished from the other regions. The feature pointsare extracted from the regions that could be recognized as the ridges.Further, an effective region for central line collation by the centralline collation part 12 is a region where the ridge regions overlap witheach other between two fingerprint images. In the following description,the effective region for the central line collation is written as acommon effective region. Further, with respect to each feature point, anending point is displayed as a circular mark, and a bifurcation point iswritten as a square mark in the drawings including FIG. 7.

A similar process is performed for the impression fingerprint as well.Then, when the feature extraction process is executed for thefingerprint image in FIG. 6, images illustrated in FIG. 8 are obtained.FIG. 8A illustrates an example where the extracted central lines aresuperimposed on the fingerprint image in FIG. 6. FIG. 8B illustrates anexample where the extracted feature points and zones are superimposed onthe fingerprint image in FIG. 6. FIG. 8 describes the images obtained bycutting off a portion of the fingerprint image in FIG. 6.

Subsequently, the central line collation part 12 performs the centralline collation (step S12). Specifically, the central line collation part12 searches for a correspondence relationship with respect to eachcentral line, using the central lines, the feature points, and the zonesin the two striped pattern images that have been extracted by thefeature extraction part 11. By searching for the correspondencerelationship for each central line, the central line collation part 12computes a ridge chart. The central line collation (ridge chartcomputation) can be implemented by a method disclosed in ReferenceLiterature 2 (Japanese Patent No. 4030829), for example.

In the method disclosed in Reference Literature 2, feature pointcollation is first performed to determine whether or not the featurepoints match to each other. FIG. 9 is a feature point chart diagramusing the feature point collation in accordance with the above-mentionedmethod and illustrates matching relationships (correspondencerelationships) between the respective feature points. Usually, nodistinction is made between feature point types (such as an ending pointand a bifurcation point) in the feature point collation. Thus, even ifthe feature points have different feature point types between twofingerprints, the feature points are determined to correspond to eachother. When FIG. 9 is checked, it can be found that eight feature pointsextracted from the remaining fingerprint have all correspondencerelationships with the feature points in the impression fingerprint. Inthe method disclosed in Reference Literature 2, a correspondencerelationship between central lines in the vicinity of feature pointswhose feature point types are different cannot be determined.

Subsequently, the ridge chart diagram display part 13 displays a ridgechart diagram by superimposing the ridge chart on each of the twostriped pattern images (step S13). FIG. 10 includes FIGS. 10A and 10Bthat constitute a ridge chart diagram illustrating correspondencerelationships between the central lines that have been subjected to thecentral line collation in the preceding step. FIG. 10A is a diagramobtained by superimposing the ridge chart on FIG. 7A, and FIG. 10B is adiagram obtained by superimposing the ridge chart on FIG. 8A. Referringto FIG. 10, the central lines (corresponding central lines) determinedto correspond to each other are displayed in thin gray, and the centrallines (noncorresponding central lines) determined not to correspond toeach other in the common effective region are displayed in thick gray.Further, the central lines outside the common effective region are thecentral lines not for checking whether the central lines are identicalor not. Thus, the central lines outside the common effective region aredisplayed in thinner gray so as not to be noticeable. To take anexample, a central line 201 in FIG. 10A and a central line 211 in FIG.10B are the (thin gray) central lines determined to correspond to eachother. A central line 202 in FIG. 10A and a central line 212 in FIG. 10Bare the (thick gray) central lines determined not to correspond to eachother.

If the two fingerprint images are a correct pair, it is preferable thatthe central lines (noncorresponding central lines) that do notcorrespond to each other be not present in the common effective region.That is, if there are the noncorresponding central lines, it isnecessary to eliminate the noncorresponding central lines by modifyingthe feature of the remaining fingerprint or the impression fingerprint.In other words, when there are the noncorresponding central lines evenif the feature has been modified, it can be said that two fingerprintsshould not be determined to be identical.

When FIG. 10 is checked, it can be seen that feature point types in thevicinity of the noncorresponding central lines displayed in thick grayare different between the remaining fingerprint and the impressionfingerprint. To take an example, the feature point positioned in aregion 301 in the vicinity of the central line 202 is an ending point.On contrast therewith, the feature point positioned in a region 302 inthe vicinity of the central line 212 is a bifurcation point.

Further, when FIG. 7B and FIG. 8B are compared, it can be seen that,among eight paired feature points in the remaining fingerprint (on theleft side of FIG. 9) illustrated in FIG. 9, the types of five pairedfeature points pertaining to (2), (3), (5), (7), and (8) are differentfrom the feature point types in the impression fingerprint.

When a user who has seen the charting screen illustrated in FIG. 9 andthe ridge chart diagram illustrated in FIG. 10 determines that thefeature with respect to one of the feature points, the central lines,and the zones that have been automatically extracted by the apparatus isnot appropriate, he tries to modify the feature. In that case, thefeature modification part 14 accepts a feature modification operation bythe user. Specifically, if the feature modification part 14 has acceptedthe feature modification operation by the user (Yes branching in stepS14), the feature modification part 14 modifies one of the featurepoints or the like of the finger print image according to the operation(step S15). The modification of the feature includes a feature pointmodification, a central line modification, or a zone modification.

FIG. 11A is a diagram illustrating an example where, with respect to thefive feature points illustrated in FIG. 9 and having the differentfeature point types, the feature point types in the remainingfingerprint have been manually modified by the user. To take an example,though the feature point type of a feature point 311 in FIG. 11A beforethe modification is an ending point (refer to FIG. 7B), the type of thefeature point is modified to a bifurcation point by the modification bythe user. With such a modification operation, the feature point types inthe remaining fingerprint are made to match those in the impressionfingerprint.

In the description about steps S14 and S15, the description has beengiven about the example where five feature point types in the remainingfingerprint are individually modified manually. Usually, an impressionfingerprint has a better quality than a remaining fingerprint. Thus, theimpression fingerprint often has correct feature point types.Accordingly, by overwriting the feature point types in the impressionfingerprint on those in the remaining fingerprint, the feature pointtypes in the two fingerprints can also be matched, without individualmodifications of the feature point types in the remaining fingerprint bythe user.

Specifically, the feature modification part 14 may overwrite the featurepoint types in the impression fingerprint on the feature point types inthe remaining fingerprint with respect to the corresponding featurepoints whose feature point types are different, using acceptance of aspecial operation (such as a feature point type overwriting instructionoperation using a menu screen or the like) by the user, as a trigger(the feature point types in the remaining fingerprint may be matched tothe feature point types in the impression fingerprint). Morespecifically, the feature modification part 14 determines whether or nota “feature point type overwriting instruction” has been input from theuser, and the feature point types in the remaining fingerprint areoverwritten by the feature point types in the impression fingerprint(step S17) if the instruction is input (Yes branching in step S16).

It is also a rational response to change, by approximately five pixels(a half of 10 pixels that are equivalent to a mean ridge interval) at amaximum, positions of the feature points in the remaining fingerprintfor which the overwriting has been performed, in consideration ofdisplacement of positions of the feature points in the impressionfingerprint after coordinate transformation. The positions of thefeature points in the impression fingerprint after the coordinateconversion can be computed by an existing triangular transformationtechnology such as a Helmert (Helmert) transformation, using coordinatesof the paired feature points extracted by the feature point collation.

If the feature has been modified in step S15, feature extraction ofholding modified feature data (manual feature) is performed (step S11).When one of the feature points has been manually modified, the featureextraction that holds the manual feature point can be implemented by amethod disclosed in Reference Literature 3 (JP Patent Kokai PublicationNo. JP-P-2016-045501A), for example. In the method disclosed inReference Literature 3, a central line that matches the manual featurepoint is generated. FIG. 11B is a diagram illustrating each central linegenerated as mentioned above. If one of the central lines has beenmanually modified, the feature point should be just extracted from thecentral line.

Subsequently, the central line collation part 12 searches for acorrespondence relationship with respect to each central line, using thecentral lines, the feature points, and the zones of the two stripedpattern images extracted by using the feature that has been manuallymodified (step S12). Since description of the central line collation hasalready given, the description will be omitted.

Subsequently, the ridge chart diagram display part 13 superimposes anddisplays a ridge chart on each of the two striped pattern images (stepS13).

FIG. 12 includes FIG. 12A and FIG. 12B that are diagrams eachillustrating correspondence relationships between the central linesafter the feature modification. FIG. 12A is a diagram that is the sameas the diagram illustrated in FIG. 11B, and FIG. 12B is a diagram thatis the same as the diagram illustrated in FIG. 8A. When FIG. 12 ischecked, it can be seen that the correspondence relationships of allridges within the common effective region have been established betweenthe two fingerprints without contradiction because no noncorrespondingcentral line displayed in the thick gray is present in either of thedrawings.

The user may modify a color type or a line type in order to distinguisheach ridge chart. Specifically, the ridge chart modification part 15accepts a ridge chart modification operation by the user (step S18). Totake an example, the user distinguishes the individual ridge charts inthe ridge chart diagram in FIG. 12 by using different colors, asillustrated in FIG. 13. When FIG. 13 is checked, it can be seen that thecorrespondence relationships between the ridges in the two fingerprintscan be readily understood even by a non-expert of the fingerprint. FIG.13 demonstrates the correspondence relationships between the ridges byusing light and dark (graduations) of the ridge charts.

As described above, the striped pattern image examination supportapparatus 10 according to the first exemplary embodiment extracts thecentral lines and the feature pints from each of the two striped patternimages and computes the corresponding central lines (ridge charts)between the images. Then, when information pertaining to thecorresponding central lines is reflected on the two striped patternimages, the striped pattern image examination support apparatus 10 takesa measure such as distinguishing the corresponding lines and thenoncorresponding lines by using the different colors, thereby allowingimmediate determination as to whether or not the two striped patternimages are from a same object to be made by the user. That is, if one ofthe noncorresponding lines is present in a region targeted for thecentral line collation, it is determined that the two images are notfrom the same object. Alternatively, even if one of the noncorrespondingcentral lines is present in the region targeted for the central linecollation, the striped pattern image examination support apparatus 10can present, to the user, information for making a decision as towhether the presence of the noncorresponding central line is caused by adifference in the feature point type or the like. When thenoncorresponding central line is changed to a corresponding central lineand no noncorresponding central line is present by a modification in arational range such as a feature point type change in this case, it isdetermined that the two striped pattern images are from the same object.

The configuration of the striped pattern image examination supportapparatus 10 (in FIG. 2) described in the above-mentioned exemplaryembodiment is an illustration and does not intend to limit theconfiguration of the apparatus. It may be so configured, for example,that the ridge chart diagram display part 13 does not display thefeature point chart diagram, and another display part is provided andthe another display part displays the feature point chart diagram.

Alternatively, it may be so configured that means (determination part)for determining whether or not one of the noncorresponding central linesis present within the common effective region is provided, and if it isdetermined by the means that no corresponding central line is present,presence of no corresponding central line is notified to the user. Thatis, it may be so configured that the striped pattern image examinationsupport apparatus 10 explicitly displays that there is no correspondingcentral line on the two striped pattern images. In this case, the needfor the user to check the ridge chart diagram and determine whether thetwo striped pattern images are from the same object is eliminated.

In the above-mentioned exemplary embodiment, the description has beengiven about a case where the feature modification that is manuallyperformed by the user (in steps S14 and S15 in FIG. 4) and the automaticfeature modification (in steps S16 and S17) by the apparatus coexist. Itmay be so configured, however, that the striped pattern imageexamination support apparatus 10 accommodates one of the featuremodifications. Alternatively, two feature modifications may becontrolled to cooperate with each other. To take an example, when anoncorresponding central line is present in the central line collationprocess after the feature modification that has been manually performed,the striped pattern image examination support apparatus 10 may performthe automatic feature modification by the apparatus. In this case, anoncorresponding central line that cannot be accommodated by visualfeature modification (feature modification that is manually performed)by the user can be set not to be present.

By installing the above-mentioned computer program in the storage partof the computer, the computer can be functioned as the striped patternimage examination support apparatus. Further, by causing the computer toexecute the above-mentioned computer program, the striped pattern imageexamination support method can be executed by the computer.

A plurality of steps (processes) are sequentially described in aplurality of flowcharts used in the above-mentioned description.However, the execution order of the steps to be executed in eachexemplary embodiment is not limited to the order in that description. Ineach exemplary embodiment, the order of the steps that are illustratedcan be subjected to a change in a range which does not cause a troubleto the contents, such as execution of the respective steps in parallel.Alternatively, the contents described in the above-mentioned respectiveexemplary embodiments can be combined in a range without inconsistency.

Part or all of the above-mentioned exemplary embodiment can be describedas the followings but is not limited to the followings.

[First Mode]

See the striped pattern image examination support apparatus according tothe first aspect.

[Second Mode]

The striped pattern image examination support apparatus, preferablyaccording to the first mode, further comprising:

a feature modification part to modify the feature of at least one of thefirst and second striped pattern images, wherein

the feature extraction part extracts a central line again while holdingthe feature of the at least one of the striped pattern images that hasbeen modified by the feature modification part;

the central line collation part computes corresponding central linesfrom the first and second striped pattern images, using the central linethat has been extracted again; and

the display part determines a display form of each of the central linesbased on the corresponding central lines that have been computed again.

[Third Mode]

The striped pattern image examination support apparatus, preferablyaccording to the second mode,

wherein when types of paired feature points respectively included in thefirst and second striped pattern images are mutually different, thefeature modification part overwrites a feature point type of one of thestriped pattern images on a feature point type of the other of thestriped pattern images.

[Fourth Mode]

The striped pattern image examination support apparatus, preferablyaccording to any one of the first to third modes, further comprising:

a modification part to accept an operation for changing, by a user, thedisplay form of the corresponding central lines in the first and secondstriped pattern images with the central lines superimposed and displayedthereon, wherein

the display part superimposes and displays the central lines on each ofthe first and second striped pattern images according to a display formthat has been changed by the user.

[Fifth Mode]

The striped pattern image examination support apparatus, preferablyaccording to any one of the first to fourth modes, wherein

the feature extraction part extracts, from each of the first and secondstriped pattern images, ridge regions including ridges and non-ridgeregions not including the ridges; and

the central line collation part sets a region where the ridge regions inthe respective first and second striped pattern images overlap with eachother to a target for the central line collation.

[Sixth Mode]

The striped pattern image examination support apparatus, preferablyaccording to any one of the first to fifth modes, wherein

the display part changes the display form of the corresponding centrallines and the display form of a noncorresponding central line(s) otherthan the corresponding central lines and superimposes and displays thecorresponding central lines and the noncorresponding central line(s) oneach of the first and second striped pattern images.

[Seventh Mode]

The striped pattern image examination support apparatus, preferablyaccording to the third mode, wherein

the feature modification part performs overwriting of the feature pointtype when a predetermined operation is input.

[Eighth Mode]

The striped pattern image examination support apparatus, preferablyaccording to the seventh mode, wherein

the feature modification part overwrites the feature point type of animpression fingerprint image on the feature point type of a remainingfingerprint image.

[Ninth Mode]

See the striped pattern image examination support method according tothe second aspect.

[Tenth Mode]

See the program according to the third aspect.

The ninth and tenth modes can be developed into the second to eighthmodes.

The disclosure of the above-mentioned Patent Literatures and so on thathave been cited is incorporated herein in its entirety by reference.Modification and adjustment of each exemplary embodiment or each exampleare possible within the scope of the overall disclosure (including theclaims) of the present invention and based on the basic technicalconcept of the present invention. Various combinations or selections ofvarious disclosed elements (including each element in each claim, eachelement in each exemplary embodiment or each example, and each elementin each drawing) are possible within the scope of the overall disclosureof the present invention. That is, the present invention naturallyincludes various variations and modifications that could be made bythose skilled in the art according to the overall disclosure includingthe claims and the technical concept. With respect to a numerical valuerange described herein in particular, an arbitrary numerical value and asmall range included in the numerical value range should be construed tobe specifically described even unless otherwise explicitly described.

REFERENCE SIGNS LIST

-   10, 100 striped pattern image examination support apparatus-   11, 101 feature extraction part-   12, 102 central line collation part-   13 ridge chart diagram display part-   14 feature modification part-   15 ridge chart modification part-   20 display device-   30 input device-   91 CPU (Central Processing Unit)-   92 memory-   93 input/output interface-   94 NIC (Network Interface Card)-   103 display part-   201, 202, 211, 212 central line-   301, 302 region-   311 feature point

What is claimed is:
 1. A striped pattern image examination supportapparatus comprising: a feature extraction part to extract at leastcentral lines and feature points from each of first and second stripedpattern images, as a feature of each of the first and second stripedpattern images; a central line collation part to perform collation ofthe respective central lines of the first striped pattern image and thesecond striped pattern image and compute corresponding central linesbetween the first and second striped pattern images; and a display partto determine a display form of each of the central lines based on thecomputed corresponding central lines and superimpose and display thecentral lines on each of the first and second striped pattern images,according to the determined display form.
 2. The striped pattern imageexamination support apparatus according to claim 1, further comprising:a feature modification part to modify the feature of at least one of thefirst and second striped pattern images, wherein the feature extractionpart extracts a central line again while holding the feature of the atleast one of the striped pattern images that has been modified by thefeature modification part; the central line collation part computescorresponding central lines from the first and second striped patternimages, using the central line that has been extracted again; and thedisplay part determines a display form of each of the central linesbased on the corresponding central lines that have been computed again.3. The striped pattern image examination support apparatus according toclaim 2, wherein when types of paired feature points respectivelyincluded in the first and second striped pattern images are mutuallydifferent, the feature modification part overwrites a feature point typeof one of the striped pattern images on a feature point type of theother of the striped pattern images.
 4. The striped pattern imageexamination support apparatus according to claim 1, further comprising:a modification part to accept an operation for changing, by a user, thedisplay form of the corresponding central lines in the first and secondstriped pattern images with the central lines superimposed and displayedthereon, wherein the display part superimposes and displays the centrallines on each of the first and second striped pattern images accordingto a display form that has been changed by the user.
 5. The stripedpattern image examination support apparatus according to claim 1,wherein the feature extraction part extracts, from each of the first andsecond striped pattern images, ridge regions including ridges andnon-ridge regions not including the ridges; and the central linecollation part sets a region where the ridge regions in the respectivefirst and second striped pattern images overlap with each other to atarget for the central line collation.
 6. The striped pattern imageexamination support apparatus according to claim 1, wherein the displaypart changes the display form of the corresponding central lines and thedisplay form of a noncorresponding central line(s) other than thecorresponding central lines and superimposes and displays thecorresponding central lines and the noncorresponding central line(s) oneach of the first and second striped pattern images.
 7. The stripedpattern image examination support apparatus according to claim 3,wherein the feature modification part performs overwriting of thefeature point type when a predetermined operation is input.
 8. Thestriped pattern image examination support apparatus according to claim7, wherein the feature modification part overwrites the feature pointtype of an impression fingerprint image on the feature point type of aremaining fingerprint image.
 9. A striped pattern image examinationsupport method comprising: extracting at least central lines and featurepoints from each of first and second striped pattern images, as afeature of each of the first and second striped pattern images;performing collation of the respective central lines of the firststriped pattern image and the second striped pattern image and computingcorresponding central lines between the first and second striped patternimages; and determining a display form of each of the central linesbased on the computed corresponding central lines and superimposing anddisplaying the central lines on each of the first and second stripedpattern images, according to the determined display form.
 10. Anon-transitory computer-readable recording medium storing thereon aprogram configured to cause a computer to execute: a process ofextracting at least central lines and feature points from each of firstand second striped pattern images, as a feature of each of the first andsecond striped pattern images; a process of performing collation of therespective central lines of the first striped pattern image and thesecond striped pattern image and computing corresponding central linesbetween the first and second striped pattern images; and a process ofdetermining a display form of each of the central lines based on thecomputed corresponding central lines and superimposing and displayingthe central lines on each of the first and second striped patternimages, according to the determined display form.